This invention deals generally with building construction and more specifically with the construction of concrete prefabricated basement walls or exterior walls for residential buildings. It relates to a method of fabricating a durable, high-strength, low cost, light weight, thermally efficient, maintenance free, and construction friendly concrete wall panel by using a corrugated thin-sheet-type bottom form permanently attached to the back of the wall panel and requiring only one pour of concrete.
Concrete walls as part of buildings, by their nature, and hurricane proof, are durable, high strength, earthquake, hurricane and flood proof, and fire resistant Concrete walls are widely used for commercial buildings such as office buildings, warehouses, factories, hospitals, theaters, stores and the like. However, traditional exterior wall materials for low-rise residential buildings such as single houses or townhouses are wood, bricks or stones but not concrete.
Three major reasons result in not using concrete exterior walls for residential buildings.
First, the construction and material cost of concrete walls is much higher than that for wooden or masonry walls. Two major construction methods for building concrete walls are cast-in-place and prefabrication.
Cast-in-place concrete wall construction employs either temporary forms or permanent forms. The temporary-forms method involves the construction of forms, either wood or metal, in the exact shape of the vertical walls, and then pouring concrete into the forms. After the concrete hardens, the temporary forms are removed and reused on other walls. On the other hand, the forms in the permanent-form method are not removed and stay in place with the wall permanently. The cost for forms limits the cast-in-place method. Although forms in the temporary-form method can be reused, the construction still involves a lot of labor work for form installation and removal.
Prefabricated concrete walls include tilt-up walls and pre-cast walls. Tilt-up walls are cast in forms on the floor slab and simply are tilted into position. This method needs a large area of very flat surface and is cost effective only in the construction of large buildings. Pre-cast wall panels are made in plants and then shipped to the job sites. The shipping cost for pre-cast panels and erection cost for both methods can be very high.
Second, concrete construction requires wall builders to be knowledgeable in concrete construction and to own or rent heavier construction equipment such as high capacity cranes. Traditionally, builders for low-rise residential buildings are familiar with wood or masonry construction, which are relatively simple and light compared with concrete construction.
Third, traditional concrete walls used in commercial buildings are made in a 3-layer sandwich structure with an insulation layer in between two concrete layers. It is not suitable for residential building because it is hard to attach interiors and utility conduits to the interior concrete layer of the walls.
Many prior art teachings show how to build tilt-up or precast concrete wall panels. For example, U.S. Pat. No. 4,856,244 to Clapp (1989), U.S. Pat. No. 6,067,757 to Olson (2000), U.S. Pat. No. 6,494,004 B1 to Zimmerman (2002), U.S. Pat. No. 6,481,178 B2 to Moore Jr., and U.S. Pat. No. 6,658,810 B2 to Deloach, Sr. All of them are creative in some ways. However, the present invention teaches a more efficient way of producing tilt-up concrete wall panels.